Imran Chaudary's 11-second...
Imran Chaudary's 11-second '69 GTO now stops as well as it goes, thanks to a cleverly designed four-wheel disc brake system that uses boneyard and over-the-counter parts, available at any parts store or GM dealer.
Go to your local wreckers...
Go to your local wreckers or GM and find a pair of rear disc brake backing plates for '98-'02 S-based two-wheel-drive trucks and SUVs. Rear disc brakes were an option in those years. These brackets also have an integrated parking brake in them. They work by expanding a brake shoe against the inner portion of the rotor. When disassembling the bracket at the wreckers, take special care to salvage the parts for the parking brake assembly. You should be able to pick them up for around $50 a pair or less.
While at the salvage yard,...
While at the salvage yard, also look for a set of brake pad retainer cages (shown with pads installed), GM PN 18026155. These items can be difficult to find, though they are available new from GM for $87.95 each.
This new dust shield from...
This new dust shield from GM costs $19.70 (each), so it makes sense to discard the old ones. Before you do, be sure to compare them to the new ones, as there are two different designs, depending on whether the backing plates locate the calipers at the 11:00 or 2:00 positions.
Prior to installing the backing...
Prior to installing the backing plate, inspect and regrease the cam for the parking brake mechanism (rubber piece on the bottom of the plate). Line up the dust shield and backing plate and bolt up to the rearend. Place a new parking brake shoe-also available at your local parts store or dealer-over the backing plate, ensuring that the open end lines up properly with the piston mechanism on the bottom of the mounting bracket.
This is how the backing plate...
This is how the backing plate and the dust shield should be oriented to mount on the righthand axle. (Parts shown from the axle side.)
This exploded view of the...
This exploded view of the S-based truck caliper shows the single piston, O-rings, pads, retaining cage, and various fittings and fasteners. These are available new from GM or remanufactured elsewhere, and the price difference is substantial.
Our diagram of the entire...
Our diagram of the entire S-based truck rearend shows a partial view of the braking system. From here, one can see how easily the backing plate can be adapted to an older rearend, as the mounting flanges are actually the same. This simple point is what makes the entire swap so straightforward.
Early Pontiac A-, B- and F-bodies have a lot going for them-great looks, powerful engines, and instant street credibility, especially for the performance versions of each series. The only real drawback is that they don't really drive like new cars. By modern standards, the handling is only so-so, and the brakes are several feet short of spectacular. True, the addition of disc brakes in 1967 did help quite a bit, but they still are not up to what one would find in a base-engined minivan. They certainly aren't adequate if even modest gains in horsepower are achieved.
Bringing performance up to modern standards is pretty much the whole idea behind the Pro Touring/G-Machine movement. Making an early GTO accelerate like a new one is not difficult-several are already there in stock form. Getting one to handle and stop like a new one, well that's a little more of a challenge-one that many are taking up and finding worth the effort. Sometimes, effective upgrades for earlier cars can come from inexpensive factory components. Whether you're building a corner-carving GTO or just want something that will stop shorter than your current disc/drum setup, we have a solution that will cost less than $500 total. You'll also be able to run a factory-style, 15-inch wheel on your car, though a 14-incher will not quite clear the caliper. Also, keep in mind that with this swap the rear track will increase approximately 11/44 inch on each side, so check your tire clearance.
Canadian GTO fan Imran Chaudary, president of the Classic GTO Club of Ontario, has developed an affordable and relatively simple rear disc brake conversion for '60s- and '70s-era GM cars that uses parts originally designed for '98-'02 two-wheel-drive compact GM pickups (Chevy S-10/GMC S-15) and SUVs (Chevy Blazer/GMC Jimmy and Envoy). The system works fo 8.2- and 8.5-inch 10-bolt and GM 12-bolt rearends. Imran has this system in his street-driven 11-second '69 GTO (a former HPP Shootout participant) and has racked up four years of trouble-free performance. Keep in mind that even though these are considered "compact" trucks, they can easily tip the scales at over 4,500 pounds, so it's not like these brake systems will be overtaxed with even the weight of a late-'60s Bonneville.
This setup is also going into club treasurer Andy Pooni's Pro Touring '65 GTO. Other club members have used this combo for their own cars and have recorded similar results. Best of all, the conversion won't break the bank and is fairly simple to accomplish.
"It's really amazing how well these new parts go together with the older rearends," Pooni says. "I guess that when it comes to pieces like rearends and axles, there is a lot of carryover from year to year and even generation to generation. When you have the critical dimensions laid out and tooling to pay for, it doesn't make sense for GM to change things if they don't have to."
When you realize that the S-10s were designed to use the same front suspension pieces as the Chevy Caprice, and the Caprice is an outgrowth of the '73-'77 A- and G-bodies, which were closely related to the '64-'72 A- and G-body platforms, you begin to see how that these seemingly unrelated vehicles actually share some vital DNA.
For this particular setup, most of the componentry can be purchased at any late-model salvage yard. The parts that Chaudary or Pooni purchased new were the wear items in the system-rotors, calipers, hoses, brake pads and the dust shields, which were available from their local dealer.
When searching through your favorite salvage yard, look for two-wheel-drive S-based compact pickup trucks and SUVs between the years of 1998 and 2001. Rear disc brakes were available on some as an option and as standard equipment on higher-end vehicles. "When Andy and I searched our yard, we removed parts for his '65 GTO from a '98 Envoy, and I removed mine from a '99 Jimmy SUV," Chaudary says. "The yard had already taken off the rotors and calipers."
Once you've found the appropriate donor vehicle, the first thing is to remove the rear axle cover to drain the fluid, as you need to slide out the axles. Keep in mind that these rearends have C-clips, so you must remove the small bolt holding the axle pin. Once the pin is out, rotate the carrier until you can get at the C-clips. Push the axles in to remove the C-clips.